Biological evaluation of pest conditions in the Big Lake Management Complex, Apache-Sitgreaves National Forests, Arizona

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92-(S68

Forest Pest

Management Report

R-3 91-6

- BIOLOGICAL EVALUATION OF PEST CONDITIONS

IN THE BIG LAKE MANAGEMENT COMPLEX
APACHE-SITGREAVES NATIONAL FORESTS, ARIZONA

MAY 1991

Department of -
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Southwestern
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United States
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BIOLOGICAL EVALUATION OF PEST CONDITIONS
IN THE BIG LAKE MANAGEMENT COMPLEX
APACHE-SITGREAVES NATIONAL FORESTS, ARIZONA

MAY 1991

By

Mary Lou Fairweather
and
di. laWilson

USDA Forest Service, Southwestern Region
State and Private Forestry
Forest Pest Management
517 Gold Avenue, SW
Albuquerque, New Mexico 87102

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ABSTRACT

The Arizona Zone Office of Forest Pest Management conducted a survey of 275
acres, delineated into five stands, in the Big Lake Management Complex on the
Springerville Ranger District, Apache-Sitgreaves National Forests. Survey
objectives were to determine distribution of insects and diseases and to use
the information to recommend a location for a proposed campground facility.
Diseases observed in the survey that could affect campground longevity and
hazard tree development were: Root rots, dwarf mistletoes, stem decays, and
aspen stem cankers. Each stand was unique in occurrence and level of these
diseases. An area within Stand 5 in which the diseases can either be avoided
or managed effectively was selected with District personnel for location of
the proposed campground.

INTRODUCTION

In 1989, Forest Pest Management in Region 3 initiated an insect and disease
incidence survey of recreation sites. These surveys were conducted to
evaluate the overall "health" of proposed and existing campground areas on
the National Forests. The Forest Pest Management Arizona Zone Office was
requested by personnel on the Apache/Sitgreaves National Forests to evaluate
275 acres in the Big Lake Management Complex, on the Springerville Ranger
District (Figure 1). The area is at 9,000 feet of elevation, and is composed
of southwestern mixed conifer species. Plans were being developed for a new
125 unit, 65 acre, mini group campground. It was necessary to determine
present pest conditions which may drive actual campground placement within
the evaluated area.

Bro LAKE

Stands
Sur veyed

) Wwe u

FIGURE 1. Stand delineation of the Big Lake Management Complex.

OBJECTIVES

The objectives of this survey were to evaluate and document the incidence of
insect and disease activity and damages in an area proposed for campground
development and to recommend a location for the proposed campground that
would have minimal pest problems.

METHODS

In the summer of 1989, five separate stands, delineated by the Ranger
District based on structure and species composition were surveyed. Although
there are actually seven stands in the analysis area south of Big Lake
(Figure 1), two of these stands (numbered 1 and 3 for identification) are
existing, developed campgrounds. The five stands surveyed are numbered: 2,
4, 5, 6, and 7 for identification. The insect and disease survey was
performed according to Region 3 Stage II Stand Exam Survey methods as
described in the Region 3 Silvicultural Examination and Prescription Handbook
(FSH 2409.26d) and as detailed for pest impacts by Terrence J. Rogers
(unpublished report). The basal area (BA) factor was adjusted appropriately
for each stand in order to obtain five to eight trees per variable plot.
Fixed plots were 1/100th of an acre. Distance between points and lines was
four chains and survey stakes were used to mark plot center.

The following data were collected for each tree recorded on the fixed and
variable radius plots: Species, diameter at breast height (DBH), height,
tree history, crown information, damage codes, and a dwarf mistletoe rating
(DMR) (Hawksworth, 1977). Age and growth increment were determined for the
first two trees on each plot.

In the spring of 1990, additional information was collected in order to
obtain root disease information and map out disease centers. The original
lines used in the first survey were cruised and the following information
recorded for each root disease center: Location to nearest plot center
(recorded in chains); size; species and DBH of live, dead, and dying trees;
symptoms (pocket-like succession of dead, dying, and fading trees) and signs
(fruiting bodies, white mycelial fans, rhizomorphs, resinosus, or incipient
decay) of root disease for each tree; type of pathogen present; and species
and approximate size of stumps. The size of the root disease center included
the approximate root radius (Filip, personal communication) of border trees
showing signs or symptoms of root disease. The proportion of the stand area
infected was estimated from the proportion of the total transect line falling
within root disease centers. The Stand Prognosis Model (Stage, 1973; Wykoff
et. al., 1982) combined with the Root Disease Model (Stage et. al., 1990) was
used to predict the effects of root disease on the future of the stands.

OBSERVATIONS
Area and Stand Structure Description

The area analyzed is in a blue spruce/Arizona fescue (PIPU/FEAR) habitat
type, containing various combinations of aspen, Engelmann and blue spruce,
Douglas-fir, ponderosa pine, southwestern white pine, and corkbark fir.
Based on data collected during the Stage II stand examination, timber type
was Classified for each stand (Table I). Stands 5, 6, and 7 classified as

aspen stands, Stand 2 spruce-fir and Stand 4 ponderosa pine. Stands
classified as aspen were not combined for analysis due to differences in
species composition and pest incidence. Basal area and trees per acre (TPA)
were lowest for Stand 5 (104 and 539, respectively) and greatest for Stand 7
(165 and 1281, respectively) (Table I). Basal area (trees >9" dbh) and TPA
in seedling, sapling, and >9" DBH classes for each species in a stand is
given in Table II. Aspen, spruce, Douglas-fir, southwestern white pine, and
ponderosa pine were found in all surveyed stands (Figure 2). True fir was
found only in Stands 2 and 4 and Douglas-fir was not found in the overstory
of Stand 6. Depending on the stand, 4 to 36 percent of the trees were found
to be infested by one or more pests (Table I).

TABLE I. Timber Type, Basal Area (BA) and Trees per Acre (TPA) of selected
stands, near Big Lake, Apache-Sitgreaves National Forest.

| | BASAL |STEM |TOTAL |Z TREE|

| STAND CLASSIFICATION] AREA/AC AC ACRES DAMAGE
{0002 |Spruce-Fir eae ete: | 990 | 87 | |
|0004 |Ponderosa ae) [oO 24-8. (4.5 | qr ae}
|0005 ~==|Aspen | 104 L535 oub M74 | |
| | | 35 | |

{0006 |Aspen 105 556 28
| 0007 Aspen 165 1281 36
140
120 : |
100 |

S

Q

ss 80 SPECIES

7 60 il ASPEN

a KS) DOUG-FIR
40 [ | PONDEROSA
5a = | | SPRUCE

[~ | FIR
. Eee

FIGURE 2. Stand Basal Areas By Species. (Trees > 9" DBH)

TABLE II. Basal area/Acre (BA), Trees/Acre (TPA), and Dwarf Mistletoe Rating
(DMR) by species.

Stand/species BA TREES PER ACRE (TPA DMR
>9" dbh <5"_dbh 5"-9"dbh >9" dbh

STAND 2 Z z z

TRUE FIR eh RG 4 oie ei ett i een PP Bi I |

SPRUCE ed i224 o.Cemeale E3203 OU wel Ea Remedy lta Omen c) aacea

PONDEROSA PINE | 11.3 9 | Greiale Bala A 3 bah nlest 3 3 ( ase

DOUGLAS SIRs ou 0| 228 :Siei24s5 Gir 212 25iegal oar nc 1 Baageee ee 3 ees

SW WHITEPINE (e123 6-105 seme Oeeie Gus | Mean lean 7 |

ASPEN oeeeLG iy ow sw lise)

TOTAL 120.3 833 81 86

STAND 4

TRUE FIR ay ie ep ye ey ie 8 |

SPRUCE 12 607 Gan ae ies COMES Ola cee] Om 53a) (gel | ne? | .2

PONDEROSA PINE |40.0 43 | 63 7 | (om 2OsmESO |

DOUGLAS-FIR (iS. Genet Jiae plamal O4casl ieee at OS Semel 10 ame? (os

SW WHITE: PINE @., |flv0se 12, -[heel3l, lowe | Abed: mele |

ASPEN Geet 0 156 19 Loa 14 ey et

TOTAL 93.3 838 30 66

STAND 5

TRUE FIR | garages aay aed | |

SPRUCE (0700 eee? eee | Wie Ae Oe aa es OR ec eS G | .6

PONDEROSA PINE |20.8 27 | 28 7 | | odlenel6 |

DOUGLAS-FIR BR ae Pa ACO AD OTe ey a 6 pee

SVRWHLTESD ENE? Al Bl 00mm G70 mele 226) on) Deu 2) |) ae. 1 |

ASPEN 26.4 34 164 42 30.37 29. 43

TOTAL 76.9 393 82 68

STAND 6

TRUE FIR | | | | l

SPRUCE Ne eh Pes Sy NT ae yh ee OSS lperaz

PONDEROSA PINE |22.8 34 | 38 10 | 4 OP WI On oI) | .6

DOUGLAS-FIR | (Pohl. doe 8] l |

SW WHITE PINE | (eh OF mse. | l

ASPEN 4 esd aimee? 12 wel? 45 57

TOTAL 67.1 372 103 78

STAND 7
TRUE FIR

| | | |
SPRUCE (26 Cameo e TIMI G Gees fe nGS, 1 63.134 e390 | .6
PONDEROGHEPINER@ 24.4) 20, CRM OMee | GSE) ol es [1.0
DOUGLAS-FIR (35.6) 29) ple? Jamel © | ie 16) 14 |
SWOWHITE PINE? 7 | 1.1) Stig |eeeaee oaee| iene 1 |
ASPEN 33. 28 345 32 34 34 45 40
TOTAL 120. 1066 100 113

edbh = diameter at breast height
Southwestern white pine

Diseases

The major diseases observed during the stand exams were: Dwarf mistletoes,
root rots, stem decays, and stem cankers. Disease occurrence varied between
stands due to differences in species composition and stand structure.

Dwarf Mistletoes

Dwarf mistletoes were the most prevalent diseases followed by root diseases,
stem decays, and stem diseases (Figure 3). Host-specific dwarf mistletoe
species (see Biology of Pests) were found infecting ponderosa pine, spruce
(Engelmann and blue), and Douglas-fir. At least two of these conifer species
were infected with dwarf mistletoe in each stand. Dwarf mistletoe infection
was not found in true fir or southwestern white pine. Dwarf mistletoe ratings
ranged from 0.1 for ponderosa pine in Stand 2 to 1.0 for ponderosa pine in
Stand 7 (Table II). This translates to light (stand DMR<0.4) to severe (stand
DMR>O.9) dwarf mistletoe infection. Dwarf mistletoes have the greatest impact
on the future species composition of a stand where an infected overstory
showers dwarf mistletoe seeds down on susceptible understory trees. In Stand 7
spruce regeneration is threatened by the spruce dwarf mistletoe: All age
classes of spruce are infected; spruce stand DMR is 0.6; and spruce seedlings
are abundant (444 TPA).

INFESTED TREES PER ACRE
BY DISEASE CATEGORY

200
150

100
DISEASE

| _| ROOT DISEASES
bad DWARF MISTLETOES
UW «sSSTEM DECAYS

[ ] STEM DISEASES

50 |f

MDO>LCHOMMDAH OMAHmnz—

2 4 5 6 7
STAND NUMBER

FIGURE 3. Infested Trees per Acre by Disease Category.

Root Disease

Root disease centers were identified and mapped (Figure 4) for all stands. The
most common root disease was armillaria root rot (see Biology of Pests) which
mainly occurred in spruce. A few annosus root disease pockets were observed on
the rocky ridge of Stand 4, around large stumps (see Biology of Pests). Root
disease pockets ranged from a single tree to a few acres of trees showing signs
and symptoms of root disease. Table III summarizes results from the
Prognosis/Root Disease Model runs. The north facing slopes of Stands 2 and 4
had the greatest percentage of acres infected (>302). Stand 7 had the greatest
number of infected trees per acre in root diseased areas, probably due to dense
stocking and the larger spruce component of the stand. Although Stand 5 had
the greatest number of infection centers, they were small (only one or two
trees) and only 12 percent of the total acres were infected. Model predictions
of future infection levels within root disease centers varied between stands.
Initially Stands 2 and 4 and Stands 5 and 6 had similar numbers of infected
TPA: 80 vs. 84 and 46 vs. 47, respectively. However, after 50 years the
predicted number of infected TPAs for Stands 2 and 4 are 27 vs. 9,

respectively, while Stands 5 and 6 were 10 vs. 13, respectively (Table III).
The variability relates to the availability of hosts as affected by species
composition and total trees per acre. The infected TPA of Stand 4 dropped off
due to a low spruce/fir component compared to Stand 2. Stands 2 and 7 are
densely stocked and have high percentages of the preferred hosts, spruce and
true fir.

LEGEND

Root disease centers

Stand boundaries

= Existing campground

FIGURE 4. Root disease centers observed in 1990.

TABLE III.

Prognosis/Root Disease Model Current and Projected Root Disease Levels.

|
[Stand |# Infection |. Acres, Infected | Total TPA® |TPA’ Infected|
hse 20 |30 (34) 45 (52) | 1034 287 | «84 ane |
Vee | 17 }14 (31) 175(38). [25984 GAG weal BO 9 «|
iis. 7} 27 | 9 (12) 13 (18) | 566 CaP I ad 2 ip |
[6. | 4 | 1 ( 3) 7h M Pe PLL ne Pe eal OM Ne ml
1281 10 10 25

erhe number of infection centers remains the same over time.
Percent of total stand acres (see Table I).
TPA = Trees per acre.

The spread rate of root disease predicted from the Root Disease Model over a 50
year period (Figure 5) shows a consistent increase for Stand 2, but
fluctuations for the other stands analyzed. In addition to species composition
and total number of trees per acre, the spread rate is also dependent on the
number of infection centers. ' The average percent of roots infected (set at a
standard 10 percent for all stands run through the model) has little effect

‘after one or two growth cycles (Marsden, personal communication). Given the
multitude of factors involved, it is difficult to interpret fluctuations in the

rate of spread. However, those stands which have high proportions of preferred
host species (i.e. spruce and true fir) have high levels of infected trees per

acre and high spread rates.

50 Year Spread Rate of
Root Disease

1.4 Jie a ee
1.2 ee a: a
F 31a" ;
E 1 ete eee 4
E
T 08 pa
/ Se ; 1
Y 0.8 : pe S08 as
E Spear Bai 4
A 0.4 Pat ony an
R | eae
0.2
0 6. -
1989 = 1999 2009 2019 . 2029 2039
YEAR
* STAND #
=f eer” 6-4 aereus} ie apa: ere

FIGURE 5. Fifty year projected spread rate of root disease of five
stands in the Big Lake Management Complex.

7

Stem decays

The major stem decay was the false tinder conk (Phellinus tremulae) in living
aspen trees (see Biology of Pests). The most common stem decay fungi in
conifers were Dichomitus squalens (Red Rot) in ponderosa pine and Fomitopsis
pinicola (Red Belt) in Douglas-fir (see Biology of Pests). These fungi are
more commonly associated with older mature trees. Infection by decays is
difficult to diagnose in live trees since most of these fungi tend to fruit on
dead woody material only. Like root diseases, stem decays are common in
developed recreation sites due to high incidences of wounds and advanced tree
age. Decay is of greater concern in these sites than in areas managed for
timber because failure of decayed trees can cause injury to people and their
property.

TABLE IV.

Average Number of Dead Trees Per Acre for each Species in a Stand.

ee 8 Oe ee 888 eee

| STAND NUMBER
|

| |
SPECIES jog? 4 5 6 7 |
ne

| TRUE FIR lemzie. 0 | | na | na | na |
| SPRUCE | wiOod lamee2 Laz [is eS {i226 |
| PONDEROSA lt nx pene i qise tat? f ges |
|DOUGLAS-FIR | 4.0 | 4.8 | nr | nr | nr |
| ASPEN [4,4 [hit ly en6 32 | 26 | e520 |
| TOTAL len 2 | a24 <1 be <O%5 [av 30 | 9.0 |

mr = none recorded
na = not applicable, species did not exist in stand

Aspen Mortality

Aspen was the species with the highest mortality rate in all stands except
Stand 6 (Table IV). Stands 2 and 4 had more than 20 dead trees per acre, with
spruce closely following aspen. Although root disease accounts for the
majority of spruce mortality, stem canker diseases were the primary cause of
aspen mortality. The most common stem diseases of aspen observed in the Big
Lake area were sooty bark (Encoelia pruinosa) and black canker (Ceratocystis
fimbriata) (see Biology of Pests). The former may girdle and kill a tree in
three to four years (Hinds and Ryan, 1985), while the latter does not girdle a
tree but typically predisposes it to windbreak. The root and butt rot fungus,
Ganoderma applanatum, was infrequently observed during the survey. This fungus
often predisposes aspens to windthrow, as the roots are severely decayed and
weakened. Like Armillaria, it also forms root disease centers.

Insects

The only insect recorded during the stand examination was the western spruce
budworm. General information on this insect is included in the Biology of
Pests section. Light defoliation (less than 25 percent of the crown
defoliated) was observed on blue and Engelmann spruce, Douglas-fir, and
corkbark fir throughout the survey area. Survey results are shown in Table V.
Trees of all diameters were affected. Spruce budworm was most common in Stand
7 (34 percent of the host trees infested) and least common in Stand 4 (6
percent of the host trees infested). In general, more budworm defoliation was
observed in the southern half of the surveyed area.

TABLE V.

Number and Percent of Trees Affected by Western Spruce Budworm

| | Trees Defoliated per Acre | Total | Percent |
| Stand | by Diameter Class | Trees | Host Trees]
| 0-4.9 5-8.9 >9 er Acre Affected |

| | | | | |
(A237 here ap: Wars co nat A nee e| PRUZ66 5% «8 | Shd2uee!
hace ee yay beisaig. @] Pat tal altos el als 30204 bai
Meets bnez0.8 PAT St wi] 11.8 | 20/57, wd! poner ty |
' 4 | TZ. feoelis).4 | 6:24 6 | 34.4 | 6.4 |

A serious outbreak of western spruce budworm is not likely to occur in the
survey area given current stand conditions. None of the surveyed stands have a
large component of true fir or Douglas-fir, the insect's principal hosts in the
southwest (Linnane, 1986). The most likely situation for the future would be
occasional light defoliation.

Although other insects were not found during the stand exam, several bark
beetle species and two aspen defoliators may occasionally occur in the area.
Four species of bark beetles: Western pine beetle, western balsam bark beetle,
spruce beetle and Douglas-fir beetle have been observed in the area (see
Biology of Pests). Spruce beetle has caused some small pockets of spruce
mortality (less than 10 trees per mortality center) in the vicinity of the
survey area in the past. One ponderosa pine, probably killed by western pine
beetle, was observed near one of the points during the survey. It is unlikely
that any of these beetles would cause extensive mortality in the survey area.
The present stand conditions are not conducive for outbreaks of any of these
beetles. Scattered single trees, primarily the largest oldest trees, may be
attacked over time.

Two species of aspen defoliators, the western tent caterpillar, and the large
aspen tortrix occur in the region. A few tents of the western tent caterpillar
were observed on aspen trees north of the survey area in the spring of 1989.

An outbreak of either of these insects could occur and cause substantial
defoliation. In that event, the main effect would be a temporary impact on
visual resources. Tree mortality following outbreaks of either of these
insects are rare. Defoliated trees usually leaf out again later in the summer
of the year they are defoliated.

BIOLOGY OF PESTS _

DISEASES

ASPEN DISEASES

Sooty Bark, Encoelia pruinosa. This canker-causing fungus is very aggressive,
causing tree mortality within four to five years after initial infection.
Disease is associated with cambial wounds; the fungus infects trunk wounds and
penetrates the inner bark and cambium. The dead outer bark sloughs off two or
three years after initial infection, exposing the blackened inner bark in an
elliptical, zonate pattern. Spores of the fungus are formed on light-grey,
cup-shaped fruiting bodies on the old, dead inner bark. Sooty-bark canker is
named for the black residue formed under the infected bark that adheres tightly
to the trunk for many years, even after tree death.

Black Canker, Ceratocystis fimbriata. This disease is widespread throughout
the range of aspen. These cankers are also associated with wounds or natural
openings in the bark. It produces black target-shaped cankers on the bole of
infected trees. This fungus seldom kills trees, because it spreads a very
short distance on the tree each year. Occasionally, two or more cankers may
eventually kill a tree by coalescing and girdling the stem. Many Ceratocystis
cankers are not associated with decay, but old cankers can weaken the tree and
cause failure. Prevention of wounds on trees will reduce the incidence of this
disease.

Aspen Trunk Rot, Phellinus tremulae. This disease is the most common cause of
defect in aspen. Fruiting bodies or conks of this fungus are frequently found
on stems of living and dead trees and often occur near branch stubs or old
wounds. Conks are hoofed shaped; the upper surface is grey to black and
divided into irregular squares by numerous cracks. The interior of the conk
has white flecks and a layered appearance; the color of the lower surface
varies from tan to white to dark brown and has many tiny pores. Trees with
more than three conks above 16 feet are generally severely decayed and
susceptible to windthrow at any time. This decay is most common in overmature
stands; however, it can also infect young trees.

White Mottled Rot, Ganoderma applanatum. A common cause of root and butt rot
of living aspen. Ganaderma applanatum is found in almost all aspen stands but
is more common on moist sites with deep soils. The fruiting bodies are
shelf-like structures, commonly called conks. A common name for this fungus is
the "artist conk" because the tissue stains permanently when bruised, and
pictures may be drawn with a sharp tool. Infections take place at wounds where
the fungus attacks sapwood, heartwood and cambial tissue. Although the decay
is typically concentrated in the large roots and basal part of the stem, it may
extend several feet up into the main stem. This root rot is usually restricted
to roots larger than 2.5 inches in diameter, indicating large roots act as
avenues of spread to new hosts. Direct mortality is minimal in most stands,
but susceptibility to windthrow can be extensive. Eighty-six percent of
windthrown aspen trees in a stand in Colorado exhibited signs of G. applanatum
at the base (Landis and Evans, 1974). Removal of infected trees is recommended
to reduce hazard in recreation sites.

10

ROOT DISEASES

Armillaria Root Disease, Armillaria spp. Armillaria root disease, or
shoestring root rot, caused by fungi in the genus Armillaria, affects several
species of conifers throughout the West. All commercial tree species in the
southwestern Region are susceptible, but nonresinous conifers, such as true
firs and spruces, are more susceptible than Douglas-fir and ponderosa pine
(Wood, 1983). Not only has susceptibility been found to vary between conifer
species, but different levels of pathogenicity (ability to cause disease) of
the fungus have been recognized. In the past, all Armillaria root disease was
attributed to one species, Armillaria mellea. However, scientists now refer to
an A. mellea complex, composed of approximately 10 distinct species which are
differentiated based on morphological, biological, and ecological properties.
While some species are purely saprophytic, decaying only dead wood material,
there are a few host specific pathogens (a parasite capable of causing disease
in a particular host or range of hosts). A. ostoyae is the species most often
associated with Armillaria root disease of conifers in the Western United
States.

Armillaria quickly invades the root system of infected trees when they are cut
or killed. The pathogen survives for decades as a saprophyte on woody tissues
of stumps and snags, which act as a food base. Spread occurs when healthy
roots contact decayed roots, or by rhizomorphs (fungal strands of hyphae) which
can grow through the soil for short distances and penetrate the bark of healthy
roots. Armillaria attacks the roots and root collar of trees of all ages,
killing the cambium and inner bark and causing a decay of both sapwood and
heartwood. Rapid death occurs when the fungus advances rapidly through the
inner bark and girdles the root collar.

The ability of Armillaria to kill trees is greatly influenced by host vigor.

It is often very aggressive in young stands less than 30 years old. The
advance of the fungus is much slower in older, rapidly growing trees, in which
resin secretion and callus formation blocks spread of disease. During periods
of drought, infected trees of all ages are often overcome. However, with a
return to average or better moisture conditions, the rate of mortality of large
infected trees nearly ceases.

Trees infected with Armillaria or other diseases are often predisposed to
attack by cambium mining insects such as Dendroctonus bark beetles, Ips, and/or
wood borers. Infestations often coincide with or immediately follow periods of
subnormal precipitation.

Armillaria root disease can be called a "disease of the site," since the
pathogen survives for extended periods of time in woody material and can infect
susceptible regeneration on the site.

Annosus Root Rot, Heterobasidion annosum. Primarily found on pines and spruce
in the Southwest. Annosus root rot can be a serious problem in plantations
that have been thinned. Heterobasidion annosum is well adapted for rapid
invasion of freshly cut stumps and is transmitted to living trees by root
contacts and natural root grafts. Basidiospores are produced from fruiting
structures, or conks, found in the root crotches or in duff around the base of
infected trees. The fungus can exist for a long time as a saprophyte in buried
roots and stumps. Symptoms are similar to other root pathogens: Dead and
declining trees, alone or in groups; and windthrown trees with decayed roots.
Control measures include: Treating the surface of freshly cut stumps with

bl

borax or urea to prevent colonization; inoculating freshly cut stumps with
highly competitive but nonpathogenic fungi; harvesting during the hot dry
summer season when conditions are adverse to spore germination and infection;
planting conifers in mixture with hardwoods; thin stands by girdling trees
rather than cutting.

DWARF MISTLETOES

Southwestern Dwarf Mistletoe, Arceuthobium vaginatum subsp. cryptopodum.
Douglas-fir Dwarf Mistletoe, Arceuthobium douglasii.

Spruce Dwarf Mistletoe, Arceuthobium microcarpum. Dwarf mistletoes are the
most damaging disease agents in Southwestern conifer forests. All dwarf
mistletoe species are host specific, but the basic biology is similar. Dwarf
mistletoes are parasitic, seed-bearing plants that depend on their hosts almost
completely for their water and nutrients. The disease spreads by explosively
released seeds which are expelled to distances ranging from 10 to 40 feet.
Seeds are released from late July through September, depending on the species.
Germination occurs in early winter of the same year as seed dispersal for
southwestern dwarf mistletoe, but occurs the following year for Douglas-fir and
spruce dwarf mistletoe. Infection takes place through the bark on
needle-bearing portions of twigs. Dwarf mistletoes first produce an endophytic
system, a specialized root-like structure that is in contact with the phloem
and xylem of host trees, from which the parasite obtains most of its nutrients
and water. The aerial shoots appear between two to five years after infection;
this period of infection before shoots are visible is known as the latent
period.

The disease causes mortality and growth reduction in infected trees: A
decrease in the quantity, quality, and germination percentage of seeds
produced; and lowers timber quality. Severely infected trees are more
susceptible to attacks by insects and other diseases and to environmental
stresses such as drought. Heavily infected trees (DMR = 5 or 6) may sustain a
20 to 50 percent reduction in growth when compared to uninfected trees and
their life expectancy is severely decreased (Lightle and Hawksworth, 1973;
Hawksworth and Geils, 1990). Dwarf mistletoe infects trees of all ages and is
thus a problem in second growth and regeneration, as well as, mature and
overmature stands.

Spread of dwarf mistletoes is a function of stand density, age, and site index,
and averages one to two feet a year. Spread is most efficient and rapid from
an infected overstory to an understory and slowest through an even-aged stand.

OTHER COMMON DISEASES OF CONIFERS

Schweinitzii Butt Rot, Phaeolous schweinitzii. One of the most common root and
brown cubical butt rot pathogens in both natural and planted coniferous
forests. Very common in old growth forests throughout the United States. Ina
study in the mountains of Arizona, it was associated with 66 percent of all
storm broken butts of Douglas-Fir (Sinclair, Lyon, and Johnson, 1987). Most
common hosts in the Southwest include: Douglas-fir, spruces, true firs, and
western white pines. Most noticeable damage is as butt rot in mature trees,
but the fungus attacks roots of any age and may enter the stems of young trees
through roots or basal wounds. The fruiting body arises from the main roots of
infected trees by means of a stalk. The fruit body is rusty yellow to brown.

12

The upper surface is tomentose or velvety from which it is called the velvet
top fungus. It is also called the cow patty fungus because it is often
mistaken for one. Phaeolous schweinitzii often enters damaged or perhaps dead
superficial roots or wounds such as fire scars at the trunk base. However,
wounds are not required. This pathogen has been reported to infect and kill
root tips and induce swelling at the ends of the resulting root stubs of
Douglas-fir. Roots previously colonized by Armillaria have also been suggested
to be avenues of infection because the two pathogens are often associated and
Phaeolous schweinitzii is capable of growing through wood colonized by
Armillaria. The opposite scenerio has been observed in Idaho.

Red Belt Fungus, Fomitopsis pinicola. A significant heart rot pathogen, unique
in that it commonly colonizes both angiosperms and gymnosperms. F. pinicola
decays both live and dead wood, but fruiting bodies are typically produced only
on dead trees and logging slash, so decay in living trees is difficult to
identify. The most common gymnosperm host groups in the Southwest include
Douglas-fir, true firs, and spruce. This is one of the most important brown
rot fungi (fungi which decay cellulose but not lignin) of old-growth western
conifers, but it acts slowly and is not considered a major decay pathogen of
second-growth forests. It is an important member of the coniferous forest
ecosystem because it decays dead trees and logging slash and leaves a
lignin-rich residue that is very stable and a major component of the forest
floor organic matter. The residue enhances water-holding and cation exchange
capacities of soil and is a favorable habitat for the development of
ectomycorrhizae and for nitrogen-fixing bacteria. The shelf-like to rounded
basidiocarps have a red-brown band near the white to cream-colored edge. The
fruit bodies are produced at wounds but it is not known if these are required
for entry.

Red Rot, Dichomitus squalens (= Polyporus anceps). Red rot is the major decay
of living ponderosa pine in the Southwest. Lightle and Andrews (1968) found
that loss due to red rot in old-growth ponderosa pine on the Navajo Reservation
in Arizona amounted to 15 percent of the gross volume. The fungus commonly
fruits on the underside of fallen logs and dead limbs. The fruiting body is
beige to yellow in color, flat, with pores from which the fungal spores are
released. Bole infections arise from infected dead branches >1 inch in
diameter with intact bark. The bark keeps moisture in the wood which aids
fungal colonization. Pruning dead limbs of ponderosa pine in recreation areas
will prevent D. squalens from infecting the bole.

INSECTS

Western Spruce Budworm, Choristoneura occidentalis. The western spruce budworm
feeds on foliage of true firs (white fir and subalpine fir), Douglas-fir, and
spruce throughout the Western United States. In the Southwest, its principal
hosts are white fir and Douglas-fir (Linnane, 1986). During outbreaks, this
moth causes considerable defoliation.

The budworm completes one generation per year. Adult flight and mating occur
in late July to early August. Females lay eggs on the undersides of needles
from late July through mid August. Following egg hatch, which occurs in about
10 days, the tiny caterpillars seek hiding places in limbs or the bole of their
host. There they spin silken shelters called hibernacula and remain for the
winter. In spring, larvae emerge and begin feeding. At first they mine buds
or older needles. As larvae mature they feed on expanding buds and fully

13

expanded current years foliage. Mature larvae pupate in silken webs. Adult
moths emerge in 10 days, completing the cycle.

Larvae feed primarily in buds and on foliage of the current year. Complete
defoliation may occur if the outbreak persists for four to five years (Furniss
and Carolin, 1977). Sustained heavy defoliation can result in decreased
growth, tree deformity, top-killing, and death. Defoliation can also
predispose trees to attack by bark beetles. Severe defoliation can affect
visual quality.

Forest stands most susceptible to western spruce budworm are multi-storied with
white fir and Douglas-fir predominating the overstory, densely stocked to
overstocked, and mature with low vigor (Linnane, 1986). Similar stands of blue
spruce, Engelmann spruce, and corbark fir are susceptible but to a lesser
degree.

BARK BEETLES

Bark beetles are small cylindrically shaped insects which bore in the inner
bark of their hosts. Most are fairly host specific. Bark beetles primarily
attack trees weakened or predisposed by factors such as drought, disease,
injuries etc., except during outbreaks. Methods that promote good growing
conditions for hosts reduce mortality rates. Four species are of minor concern
in the area surveyed.

Western Pine Beetle, Dendroctonus brevicomis. Western pine beetles attack
ponderosa pine in the Southwest. Trees six inches and larger may be attacked
(Demars and Roettgering, 1982). This insect most commonly attacks old trees,
or younger trees if growing in dense stands. Trees recently hit by lightning,
or heavily infected with southwestern dwarf mistletoe are also frequently
infested. Two to four generations of beetles are produced per year. The
beetles are active from late spring until the onset of cold weather in fall.
Galleries are winding or mazelike in appearance. The best external evidence of
infestation is the presence of pitch tubes on the bark surface.

Western Balsam Bark Beetle, Dryocetes confusus. The western balsam bark beetle
attacks corkbark and subalpine firs in the Southwest. Its biology is not as
well known as some other bark beetles. It is frequently observed in
association with root disease centers. A one to two year life cycle is
reported (Furniss and Carolin, 1977). Egg galleries consist of a central
nuptial chamber with several egg galleries radiating out.

Spruce Beetle, Dendroctonus rufipennis. The spruce beetle attacks Engelmann
spruce primarily and blue spruce infrequently in the Southwest (Schmid and
Frye, 1977). It prefers downed material to standing trees, but when the former
are unavailable standing trees may be attacked. Large diameter standing trees
are preferred to small trees.

This insect has a two year life cycle. Adults attack in June and July and the
first winter is passed in the larval stage. Development continues the second
year and by the second winter the adult stage is reached. The adults emerge
the following summer. Egg galleries are oriented parallel to the wood grain
with a slight curve in the initial portion. Best external evidence is the
presence of reddish-brown boring dust or occasionally pitch tubes on the bark
surface.

14

Unmanaged stands of Engelmann spruce and subalpine fir may be rated tor
susceptibility to this insect using a system developed by Schmid and Frye
(1976). Four stand characteristics: Average diameter of spruce, basal area,
species composition, and physiographic location are used for rating.
Potentially high risk stands would have an average DBH of greater than 16
inches, basal area of more than 150 square feet per acre, more than 65 percent
spruce in the canopy and located in a well drained (good site) creek bottom.
Low risk stands usually have an average diameter of less than 12 inches, basal
area of less than 100 square feet per acre, less than 50 percent spruce in the
canopy, and a site index of 40-80.

Douglas-fir Beetle, Dendroctonus pseudotsugae. Douglas-fir is the only host
for this insect in this Region. Downed trees as well as standing trees are
attacked. In the Southwest, outbreaks have been associated with western spruce
budworm outbreaks. Greatest mortality occurs in dense stands of mature trees
(Furniss and Orr, 1978).

One generation is produced per year. New attacks usually occur between April
and June. Egg galleries run parallel to the wood grain and average 8 to 10
inches in length. Reddish-brown boring dust caught in bark crevices is good
evidence of attack. No pitch tubes are formed but resin may stream from the
attacks in the upper bole.

ASPEN DEFOLIATORS

Western Tent Caterpillar, Malacosoma californicum.

Large Aspen Tortrix, Choristoneura conflictana. Both of these moths are
defoliators that feed on aspen in the Southwest. A one year life cycle is
reported for both species. Larvae primarily feed in spring on aspen foliage.
Western tent caterpillar larvae produce large silken tents in which they feed.
Aspen tortrix larvae first feed within aspen buds in spring and later roll
leaves into feeding shelters. Outbreaks of both insects are relatively
short-lived and result in minor damage even though whole trees can be
defoliated. Occasionally sustained outbreaks (four years or longer) of western
tent caterpillar have resulted in tree mortality and top-killing (Jones et al,
1985).

15

MANAGEMENT CONSIDERATIONS

Recreation sites should be developed in areas where existing or potential
insect and disease incidence does not conflict with management objectives. It
is extremely important to consider the longevity of the site and projected
hazard tree development. Managers must decide what pest infested areas to
avoid (eg. a highly dwarf mistletoe infected stand) and when silvicultural
treatments may alleviate pest problems, especially if visual quality or design
objectives are enhanced. For example, root disease infected trees and their
stumps can be removed from an area with a few small root disease centers. The
cleared area can be used for an administrative center or parking lot. Another
example is pruning and removing dwarf mistletoe infected trees in areas where
infection is very light and the majority of the site is occupied by nonhost
type trees. Control treatments to consider for the major pests found in the
Big Lake Management Complex are offered below.

In the summer of 1990, Recreation Management personnel on the Apache-Sitgreaves
National Forests met with staff from the Forest Pest Management Arizona Zone

to review the results of our survey and select a general area for development
of the campground. Consideration was given to the incidence and distribultion
of disease in addition to campground design and construction criteria. As a
result, an area within Stand 5 was selected and is shown in Figure 6.

LEGEND

Area selected

KN
ei

#'s = Deliniated stand number

Root disease centers

CG = Existing campground

Figure 6. Preferred Area of Stand 5 for Campground Development.

Armillaria Root Disease

In southwest mixed conifer forests, a large proportion of tree mortality is
attributed to root diseases and associated pests (Wood, 1983). Armillaria root
disease can be called a "disease of the site," since the pathogen survives for
extended periods of time in dead woody material and can infect susceptible
regeneration on the site. Careful examination and mapping of infection centers
in the Big Lake Management Complex was necessary to identify areas to avoid or
in need of special treatment. The preferred area for campground development
has a few small root disease centers.

16

Treatment recommendations are best directed toward limiting disease buildup or
reducing its impact. Treatment options include: Minimizing stress to and
wounding of residual trees; reducing the food base of the fungus by uprooting
infected stumps; reforesting heavily infected stands with less susceptible
conifers; and maintaining vigorous tree growth. It is best to avoid developing
recreation sites in root disease infected areas. However, as mentioned above,
small diseased centers (1 to 10 trees) may be cleared for administrative or
parking areas, where the trees and stumps are removed. The disease may be
found on trees 30 to 40 feet beyond the last visibly infected tree. A buffer
zone should be treated along with the obvious infection center. Pathogenic
Armillaria species do not colonize uninfected dead root systems, therefore,
cutting a buffer strip of healthy trees should halt the spread of disease.

Pushing out stumps with heavy machinery may also be used to protect
regeneration. Emphasis on less susceptible hosts such as southwestern white
pine is recommended. Where the emphasis is on visual quality and not site
development and aspens are adapted to the site, species conversion to aspen
over the rotation allows Armillaria to die out in conifer roots and stumps.

DWARF MISTLETOES

The first step in management of dwarf mistletoe is to determine the level of DM
acceptible to accomplish management objectives for a given area. Constraints
such as costs, appearance of treatments, suitability of site, etc., are also
considered. Dwarf mistletoe in developed recreation sites should be avoided.
However, if the level of disease is low in a host species which represents a
small percentage of the total trees per acre, treatment during construction may
be considered. Followup treatments are required.

Treatments are typically directed toward decreasing spread and intensification
of disease since dwarf mistletoe eradication is achieved only by removing the
entire stand of trees. In timber emphasis areas, treatments include
regeneration cuts, in which infected residuals are removed after stand
establishment, and intermediate thinnings which remove the more heavily
infected trees.

In recreation forests, pruning is an alternative treatment to decreasing
infection and prolonging the life of valuable trees. The following suggestions
for southwestern dwarf mistletoe control in recreational forests are offered
based on a 20 year study in Grand Canyon National Park by Lightle and
Hawksworth (1973):

- Pruning is recommended in lightly infected trees (DMR<3). Remove
branches two whorls above highest DM-infected branch to insure against
latent infections. No more than 50 percent of the live crown should be
removed.

- Confine pruning to more isolated trees. Repruning has been required in
densely stocked stands due to numerous latent infection in areas
initially considered lightly infected.

- Infected branches should be cut off at the bole in order to insure
removal of the root-like, endophytic system in the host tissue.

- Trees with bole infections do not need to be killed since bole
infections are not vigorous.

iW

- Pruning witches brooms on heavily infected trees (DMR = 3-4) does
prolong life. A shorter life expectency corresponds to higher DMR.

Other management strategies include:

- Sanitize densely stocked stands. The most severely infected trees are
removed to eliminate much of the inoculum and promote vigor of lightly
and non-infected trees. .

- Remove severely infected overstory trees. A vegetation management plan
should be prepared for the recreation site in which long-term
maintenance of tree cover is stressed; emphasize non-host species to
eventually replace dwarf mistletoe-infected trees.

- Apply ethylene-releasing chemicals to promote abscission of dwarf
mistletoe aerial shoots (Beatty, et. al., 1988; Nicholls, et. al.,
1987). This method may reduce seed dispersal; the pathogen is not
eliminated since the endophytic system remains viable within the host
tissue and new aerial shoots continue to form, even the same year plants
are sprayed (Johnson and Hildebrand, 1990). Research is in progress to
assess the effects of this method for controlling dwarf misltetoe seed
dispersal and protecting high value trees from becoming infected.

OTHER COMMON DISEASES OF CONIFERS

The same levels of root and stem decay desirable in old growth forests, create
hazard trees which may lead to injury to people and/or damage to their property
in developed recreation sites. Avoiding sites with extensive decay is one
approach to this problem, however, investigations have shown that recreation
use itself increases the incidence of root and stem disease fungi (Storozhenko,
1987). A preventive approach is desirable and would include: site
construction which limits wounding; design which will limit soil compaction
over tree roots; a plan to educate the recreationist on the consequences of
injuring trees; pruning dead limbs of mature pine to prevent fungi from
infecting the bole. Most stem fungi get established in limbs greater than one
inch in diameter and are associated with older, mature trees.

ASPEN DISEASES

Developing campgrounds in areas where greater than 30 percent of the trees are
aspen is highly discouraged. The life expectancy of a campground in an aspen
grove is only 25 to 30 years (Hind, 1976) and costs of hazard tree removal are
high. A recent study in New Mexico (Rogers, 1990), reported over 500 dead
aspen trees in a 29-year-old developed site. The bark of aspen is very thin,
making these trees highly susceptible to diseases and insects. Mechanical
injuries sustained as a result of site construction and recreationists, and
sunscald injury from stand openings (Walters, et. al., 1982), creates entry
courts for disease causing fungi. These fungi are the main cause of mortality
in aspen. An area with a small percentage of aspen can be utilized if the
aspens are not located in high use areas.

We recommend a preventive approach to development of the campground in the Big
Lake Management Complex and suggest a vegetation management plan for the entire
area be developed. A preventive approach would, most importantly, include
careful site selection which considers minimal pest impact. Avoiding areas
with aspen as the dominant species is crucial.

18

REFERENCES

Beatty, J.S., H. Maffei, E. Collins, and M. Christian. 1988. Ethephon tests
for ponderosa pine dwarf mistletoe in New Mexico. Proceedings of the 36th
Western International Forest Disease Work Conference, p 39-40.

Demars, C.J., and B.H. Roettgering. 1982. Western pine beetle. Forest Insect
and Disease Leaflet 1, USDA Forest Service, 8 p.

Furniss, R.L., and V.M. Carolin. 1977. Western forest insects. USDA Forest
Service Miscellaneous Publication No. 1339. 654 p.

Furniss, M.M., and P.W. Orr. 1978. Douglas-fir beetle. USDA Forest Service
Forest Insect and Disease Leaflet 5. 4 p.

Hawksworth, F.G. 1977. The 6-class dwarf mistletoe rating system. USDA
Forest Service, Gen. Tech. Rep. RM-48. 7 p. Rocky Mountain Forest and Range
Experiment Station, Fort Collins, CO.

Hawksworth, F.G. and B.W. Geils. 1990. How long do mistletoe-infected
ponderosa pines live? Western Journal of Applied Forestry 5:47-48.

Hinds, T.E. 1976. Aspen mortality in rocky mountain campgrounds. USDA Forest
Service, Gen. Tech. Rep. RM-164. 20 p. Rocky Mountain Forest and Range
Experiment Station, Fort Collins, CO.

Hinds, T.E. and M.G. Ryan. 1985. Expansion of sooty-bark and ceratocystis
cankers on aspen. Plant Disease 69:842-844.

Johnson, D.W., and D.M. Hildebrand. 1990. Effects of application rate and
timing of ethephon treatments on abscission of ponderosa pine dwarf mistletoe
two years following treatment. USDA Forest Service, Gen. Tech. Rep. R2-47.

9 p. Rocky Mountain Region, Lakewood, Colo.

Jones, J.R., N.V. Debyle, and D.M. Bowers 1985. Insects and Other
Invertebrates. In: DeByle, N.V., and R.P. Winokur, eds. Aspen: Ecology and
Management in the Western United States. USDA Forest Service General Technical
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Fort’ Collins;*Cco.,

Landis, T.D. and A.K. Evans. 1974. A relationship between Fomes applanatus
and aspen windthrow. Plant Disease Reporter 58:110-113.

Lightle, P.C. and S.R. Andrews. 1968. Red rot in residual ponderosa pine
stands on the Navajo Indian Reservation. USDA Forest Service, Res. Pap. RM-37.
12 p. Rocky Mountain Research Station, Fort Collins, CO.

Lightle, P.C., and F.G. Hawksworth. 1973. Control of dwarf mistletoe in a
heavily used ponderosa pine recreation forest: Grand Canyon, Arizona. USDA
Forest Service, Res. Pap. RM-106. 22 p. Rocky Mountain Forest and Range
Experiment Station, Fort Collins, CO.

19

Linnane, J.P. 1986. Integrated forest protection guide. Western spruce
budworm in the southwest. USDA Forest Service Forest Pest Management Report
R-3 86-7. 22 p. Southwestern Region, Albuquerque, NM.

Nicholls, T.H., L. Egeland, F.G. Hawksworth, and D.W. Johnson. 1987. Gontrol
of dwarf mistletoe with ethephon. Proceedings of the 34th Western
International Forest Disease Work Conference, p. 78-85.

Rogers, T.E. 1990. Biological evaluation of pest conditions and potential
hazard trees occurring within the Canjilon Lakes recreation area. Carson
National Forest, New Mexico. USDA Forest Service, R-3 90-6. 18 p.
Southwestern Region, Albquerque, New Mexico.

Schmid, J.M. and R.H. Frye. 1976. Stand Ratings for Spruce Beetles. USDA
Forest Service Research Note RM-309. 4 p. Rocky Mountain Forest and Range
Experiment Station, Fort Collins; C03

Schmid, J.M. and R.H. Frye. 1977. Spruce Beetle in the Rockies. USDA Forest
Service General Technical Report RM-49. 38 p. Rocky Mountain Forest and Range
Experiment Station, Fort Collins ycco.

Sinclair, W.A., and H.H. Lyon, and W.T. Johnson. 1987. Diseases of trees and
shrubs. Cornell Uiversity Press. 574 p.

Stage, A.R. 1973. Prognosis model for stand development. USDA Forest
Service, Res. Pap. INT-137. 17 p. Intermountain Forest and Range Experiment
Station, Ogden, UT. .

Stage, A.R., C.G. Shaw, M.A. Marsden, J.W. Byler, D.L. Renner, B.B. Eav, P.J.
McNamee, G.D. Sutherland, and T.M. Webb. 1990. User's manual for western root
disease model. USDA Forest Service, Gen. Tech. Rep. INT-267. 49 p.
Intermountain Research Station, Moscow, Idaho.

Storozhenko, V.G. 1987. Fungus diseases in recreation forests. Lesnoe
Khozyaistro. No. 3, Ru, 7 ref. VNILM, USSR.

Walters, J.W., T.E. Hinds, D.W. Johnson, and J. Beatty. 1982. Effects of
partial cutting on diseases, mortality, and regeneration of Rocky Mountain
aspen stands. USDA Forest Service, Res. Pap. RM-240. 12 p. Rocky Mountain
Research Station, Fort Collins, CO.

Wood, R.E. 1983. Mortality caused by root diseases and associated pests on
six National Forests in Arizona and New Mexico. USDA Forest Service, R-3
83-13. 31 p. Southwestern Region, Albquerque, New Mexico.

Wykoff, W., N.L. Crookston, and A.R. Stage. 1982. User's guide to the stand

Prognosis model. USDA Forest Service, Gen. Tech. Rep. INT-133. Lizgap:
Intermountain Forest and Range Experiment Station, Ogden, UT.

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